Companies have embarked on a gradual but massive adoption of Internet of things (IoT) technology, investing in sensors to collect data, which is then wirelessly sent for further analysis or alerts, according to a survey.

IoT involves hardware, like small devices and wireless networking, as well as software, but sensors are key for extracting data from objects and the environment, said PwC in the survey, released Monday.

“From refrigerators to parking spaces to houses, the IoT is bringing billions of things into the digital fold, which will make the IoT a multi-trillion dollar industry by 2020,” PwC said in an executive summary of the survey.

Twenty percent of companies are investing in IoT sensors, up from 17 percent last year. The survey is based on responses from almost 1,500 company executives.

Fourteen percent of the respondents said sensors are of top strategic importance to their companies in the next three to five years.